At present, a range of mechanical, magnetic and electronic switches may be provided on or attachable to valves to provide an indication as to when a valve is fully open or fully closed, however, it has not been possible to accurately indicate intermediate positions of the valve stroke in a simple and economical way.
For instance, different types of valve have different flow characteristic curves relating percentage flow through the valve against percentage opening of the valve, so that even if the percentage opening of several different types of valve was the same, then widely differing flow rates result and thus make it extremely difficult for simple mechanical, magnetic and electronic devices, which measure the actual opening of the valve, to give a precise indication of the flow rate through the valve.
Further, for a given pressure and valve opening, changes in the temperature and viscosity of the fluid alter the flow performance which is difficult to compensate for with simple arrangements, and with very viscous fluids, if the temperature drops below a certain critical point, then viscosity may increase to an extent at which flow will cease altogether.
The aim of the present invention it to provide a device capable of ascertaining flow rate through at least one valve simultaneously and displaying said flow rate or utilising said flow rate to control said at least one valve.